This invention relates to the recovery of nitrated esters from water. In another aspect this invention relates to purification of the wash or process water of explosive manufacturing processes where it is desirable to recover substantially all of the nitrated esters contained in the water prior to its release. Still another aspect of this invention relates to the separation of an aqueous solution which contains minor amounts of nitrated esters of polyalcohols which are only slightly soluble in water.
The commercial production of glyceryl nitrate (also known as nitroglycerin) and ethylene glycol dinitrate, for example, for explosive compositions normally involves operations including nitration, separation of spent nitric acids and purification by neutralization and washing. During the purification and washing steps, large volumes of water are used which come into contact with the nitrated esters. Because the solubility of these nitrated esters in water is very low, the water and a major portion of the nitrated esters can be separated easily. However, a limited quantity of the nitrated esters is dissolved in the wash or process water and heretofore has been discharged with the water phase. Presently, the water effluents only contain the amounts of nitrated esters which can be dissolved in the water. That is, for reasons of safety, the effluent water contains amounts of nitrated esters which do not exceed the saturation point of the water at the temperature at which it is discharged. Recently, however, the Environmental Protection Agency has proposed more stringent effluent limitations and guidelines regarding the maximum COD (chemical oxygen demand) and BOD (biological oxygen demand) which effluents from explosive manufacturing plants may have. See EPA Proposed Regulation, Section 457.10-457.12, 41 Fed. Reg. 10184 (1976). Because COD requirements are directly related to the concentration of the nitrated esters in the effluent water, a process for the removal of nitrated esters which have become dissolved in the water is desirable.